1. Field
The present invention relates to a perpendicular magnetic recording medium and a magnetic disk device having it.
2. Description of the Related Art
In recent years, with the increase in the track density of hard disk drives (HDDs), recording heads have come to form narrower tracks. However, where such a narrow-track recording head is used, the intensity of a recording magnetic field generated by the tip of the recording head may be made so low that recording magnetization having a sufficiently high S/N ratio (signal/noise ratio) cannot be written on a medium.
To increase the intensity of a recording magnetic field, it has been attempted to set the recording head closer to the medium. However, there is a technical problem that if the recording head comes too close to the medium, devices in the HDD suffer physical deterioration because of contamination that is caused by frictional wear of the recording head and the medium.
To solve the above problem, a magnetic recording medium has been proposed which is provided with a main recording layer having such perpendicular magnetic anisotropy that the anisotropic magnetic field strength is Hk1 and the inclination of a magnetization curve at an inversion point is α1 and a writing assistance layer which is formed so as to be in contact with the main recording layer from above or below and whose anisotropic magnetic field strength is Hk2 and inclination of a magnetization curve at an inversion point is α2, wherein relationships Hk2<Hk1 and α2>α1 are satisfied.